I have a whole chapter on the subject in my
CorelDRAW X3 book. http://www.unleash.com/coreldrawx3unleashed/ . There is no "simple" answer. If you are looking for a magic button to
push, you won't find it. The best way is to redraw the image and this isn't
nearly as hard as you think. If you just want the info from that single chapter,
you can get it at http://www.unleash.com/articles/vectorize/ though I bet the rest of the book would be very valuable for you to
have.